If the files are web based I'd try this:
In order for this process to work it is essential that the .pdfs have a URL that is stored on the web, and that the URL for each .pdf resides in your database data. This way a URL action can be created in Tableau Desktop that pulls the image of the .pdf from the web into your dashboard based on user selection of projects within your dashboard.
To create a URL action that points to a web-based resource:
1.Drag “Web Page” from the left hand tool bar onto your dashboard to create a dynamic web page window.
2.From the menu at the top of your dashboard, go to “Dashboard,” and then navigate to “Actions” in the dropdown menu.
3.Click on “Add Action” in the pop-up window and navigate to “URL” in the dropdown menu.
4.Give your action a useful name in the “Name” field.
5.Under “Run action on:” choose “Select.” This indicates that the action occurs when the user clicks on a selection.
6.Click on the triangle to the right of the “URL” field, and select the name of the column (from your data) that the unique URLs reside in.
7.Click on “OK.”
If the files are local you should be able to do this with some limitations by following the instructions below:
1. Whitelist "file" in Tableau Server
-- a. Click the Start button, and then select All Programs > Accessories. Right-click Command Prompt and select Run as administrator.
-- b. Navigate to the bin directory of Tableau Server.
-- c. Stop Tableau Server using this command: tabadmin stop
-- d. Whitelist "file" using this command: tabadmin set vizqlserver.url_scheme_whitelist file
-- e. Start Tableau Server using this command: tabadmin start
2. Whitelist the file path in Internet Explorer (This is a precaution for locked down environments)
-- a. Open Internet Explorer
-- b. Select Tool > Internet Options
-- c. Navigate to the Security tab
-- d. Select Local intranet
-- e. Select Sites > Advanced and add the file path
-- f. Select OK and restart Tableau Server
3. Create a URL action in Tableau Desktop
-- a. Open Tableau Desktop
-- b. Create a dashboard
-- c. In the dashboard select Dashboard > Actions...
-- d. Select Add Action > URL...
-- e. Rename the filter and select the source sheet for the action.
-- f. In URL place the file path start with file://
Example: file://filesrv01/Public/drahm/Example Space.txt
-- g. Publish the workbook to Tableau Server
This will only work using Internet Explorer. Firefox and Chrome do not allow access to local file systems as a security measure. It should also be pointed out that Internet Explorer will interpret an FQDN as an internet connection. Internet connections do not have access to the file system.
This knowledge-base article may also be helpful:
I hope this helps!